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Graphics & Text Images 1. Screen Frequency (100 lpi) & Image Resolution (200 dpi): |
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We generally
produce our plates at 100 lpi / 1270 dpi. The resolution of an image
needs to be at least 1.5 to
2 times the screen frequency resulting in
a 150 dpi (minimum) to 200 dpi (preferred) at full size. Note: Resolution higher than 200 dpi will not significantly
improve the quality of the image, but will result in a much larger file
size.
Line art
should be 600 dpi.
Vector images are created with mathematical
formulas and can be enlarged without affecting print quality. (Freehand,
Illustrator and CorelDraw create vector images). |
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2. Generating Separations - Grayscale,
CMYK, Spot:
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Grayscale Images - make sure that images that are meant to print
black or grayscale are truly built as a grayscale file. On screen an
image may appear to be black but if it is in CMYK mode it may take all
four plates to create that color. This is called a rich black and can
create two problems on our press: 1) tracking - if the ink density is too high then the image
may track to other pages throughout the book when the paper touches
on press 2) registration - if registration is off slightly, you
may see a halo of color around the image |
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| Now, if you have an image where parts of it are color,
therefore cannot be grayscale, there is a trick in Photoshop that can
easily take the color out of just the black elements. |
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Go into the Color Settings dialog box,
listed on the previous page, and change the black generation to GCR/
Maximum Black. Click OK. Change the color mode of your image to RGB.
Then, change it back to CMYK. By doing this, Photoshop converts the
high ink density areas to a solid black instead of a build of all four
plates. Note: Make sure that you switch the
Color Settings back to your original settings, listed on previous page,
for all other images. |
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CMYK Images - Our press
uses four plates to produce full color images: Cyan, Magenta, Yellow
and Black. We recommend that all color images, excluding spot colors,
be CMYK rather than RGB. This will give you more control of your images
and let you see a better representation on your screen. Spot Images - Spot images can sometimes be tricky to work with. If
spot color is used it is essential that you assign it as spot in the
application and that the name of the spot matches exactly. For example,
if you are using PMS 201 CVU, then make sure that it is named exactly
the same way in all applications that are used, like Quark, Photoshop,
Illustrator, etc... 3. Dot Gain: |
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Other things to watch out for... 1. Rules should be at least .25 points thick or they may
not show up on plate. 2. Stay away from small or thin type if it knocks out of
color because it may fill in due to dot gain. |
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3. If your are using .eps files within your document, make
sure that fonts are embedded or converted to curves. 4. Yellow can be hard to read by itself when printed on
newsprint so we suggest adding a 10% magenta unless the yellow is on
top of another color. |
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5. If you are choosing a spot color out of a pms book do
not use the top three colors because they require a mix of 50% white
or more which will result in light ink and the ink coverage will not
print evenly throughout the book. 6. When using background screens with type that is black
or the same color as the screen, the screen should be a maximum of 30%.
If the screen is darker than a 30%, the type may be hard to read. Screens
should be a minimum of 10% because anything lighter may not show up
as much as you’d like. |
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